Boto3 SDK missing from Python3.8

[mdavis-xyz]

Summary

I expect both build and run containers to have boto3 pre-installed, since there's a version of boto3 pre-installed in real lambdas.

Note that the exact versions of boto3 and botocore that should be installed can be found here.

Steps to reproduce

Build this image:

FROM lambci/lambda:build-python3.8
RUN python3 -c 'import boto3'

Expected behavior

Image build sucessfully. i.e. boto3 is already installed

Actual behavior

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'boto3'